Fine Time Measurement based Time Synchronization for Multi-AP Wireless Industrial Environments

abstract

Industrial networks rely on Ethernet and its complementary Time Sensitive Networking standards to support critical application requirements such as bounded latency and low jitter. To meet these requirements, precise time synchronization across wired devices is typically achieved across the wired devices via the Precision Time Protocol (PTP). PTP as a UDP-based protocol can synchronize wireless devices as well, provided that these guarantee hardware-based timestamping. On the other hand, Wi-Fi integrates time synchronization mechanisms better suited to its shared medium, such as the the Fine Time Measurement (FTM) protocol. Aiming at contributing to the time synchronization solution across multi-AP industrial environments, this paper proposes a hiearchical FTM-based synchronization approach capable of supporting time synchronization in a way compatible with Ethernet/TSN. The evaluation of the proposed solution carried out with the ns-3 DetNetWiFi framework, shows that it successfully synchronizes all devices within the networ with an accuracy of less than 5 μs and providing fairness in terms of balancing FTM requests in dense networks effectively.